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Hospitalization (ashore or at sea) caused by, or suspected to be associated with, influenza or ILI onboard the vessel.

In addition, CDC is taking this opportunity to emphasize that any death, including those caused by, or suspected to be associated with, influenza or ILI, that occurs aboard a cruise ship destined for a U.S. port must be reported to CDC immediately. Report ILI hospitalizations or deaths by submitting an individual
Maritime Conveyance Illness or Death Investigation Form [PDF - 4 pages]
for each hospitalization or death, or report by phone.

An outbreak is occurring if the total number of cases of influenza or ILI on a cruise ship among passengers OR crew exceeds the threshold of 1.380 cases per 1,000 person-days, as calculated below. This threshold is based on Alaska regional data from 1998.*

d = number of days onboard the voyage at the time of reporting to Q Station,

where equation for d = [Report to Q Station Date – Departure Date (1st day of voyage)]

Theshold Calculation:

n = (1.38)(p X d) ÷ 1,000

The actual number of ill cases reported should be greater than n to be considered an outbreak.

Examples

Example 1: How do you calculate the passenger threshold?

A ship with 1,200 passengers onboard for 21 days reports 30 passenger cases

p=1,200

d=21

n=(1.38)(p X d)/1,000=(1.38)(1,200 X 21)/1,000 = 34.8

Since 30 (the number of cases), is less than 34.8 (the ILI threshold), the threshold (n) has not been reached

Example 2: How do you calculate the crew member threshold?

The same ship with 800 crew members onboard for 21 days reports 25 crew member cases

p=800

d=21

n=(1.38)(p X d)/1000=(1.38)(800 X 21)/1,000 = 23.2

Since 25 (the number of cases), is greater than 23.2 (the ILI threshold) the threshold (n) has been reached

*Bodnar UR, Maloney SM, Fielding KL, et al. Preliminary guidelines for the prevention and control of influenza-like illness among passengers and crew members on cruise ships. Atlanta: US Department of Health and Human Services, 1999.